Use algorithms, code segments, procedure to define the geometry of your
object.

Add as much physics or art as you want

Advantages: flexibility, data amplification, procedural abstraction.

Examples:

Volume
metaball Cloud
This image is a volume rendered and procedural altered metaball. The image
has low-albedo gas illumination and atmospheric attenuation.

My
version of the blizzard of '96
This image shows how metaballs, volume swirling snow, and polygonal models
can be combined to produce great images. You could say that during the
blizzard I created a virtual snowman and my own blizzard.